JP2903882B2 - Stencil mask forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam and electron beam lithography technology for fine processing of a semiconductor device, and more particularly to a stencil mask in a reduced batch transfer type electron beam lithography using a stencil mask. It relates to a forming method.

[0002]

2. Description of the Related Art Electron beam lithography has been used as a tool for advanced development of LSIs because it does not require the use of a reticle and can form a fine pattern. 2. Description of the Related Art Conventionally, an electron beam writing method widely used is a method in which patterns are sequentially drawn one by one by a Gaussian beam (point beam) or a variable shaped beam using a field emission or thermionic electron gun. Yes, so-called single stroke method. That is, an electron beam generated from an electron gun can be focused on a resist surface by a focusing lens into a narrow beam spot, and the position of the beam spot can be controlled by a deflection system to draw an arbitrary figure on the resist. It is. This method has the merit that distortion and aberration inside the deflection field can be electrically corrected and the accuracy can be increased depending on the control technique, and many methods have been developed and put to practical use. For example, H. J. King and others Jou
rnal Vacuum Science and T
technology B3 p. 106 (1985)
As shown in (1), a fine pattern of 0.5 μm or less can be arbitrarily formed by using the graphic data by using the electron beam direct writing technique. However, on the other hand, in this method, since the spot diameter of the electron beam is about 0.1 to 2 μm, the size of the drawing pattern is reduced, and the number of spots to be drawn becomes enormous. Graphic data also has a very large data amount. There is also a drawback that the spot movement speed is limited due to the limitation of the operating frequency of the deflection system, and the time required for drawing becomes extremely long, and the throughput is reduced.

In order to solve these drawbacks, recently, a reduced transfer method in which a pattern of a partial repetition pattern is collectively transferred using a mask, instead of drawing all the patterns of an LSI chip as a single stroke, is used. A way was figured out. In other words, there is a method in which a repetitive area of the LSI pattern is decomposed into small area partial patterns, this pattern is formed on a stencil mask, and the pattern is sequentially transferred using this mask. However, this method is expected to have a very high throughput, but it is very difficult to form a stencil mask to be used. For example, an example of a stencil mask processing method currently considered is shown in FIG.

An acceleration voltage of 50 to 50 is applied to the semiconductor silicon substrate 11.
Boron ions 42 are implanted at 100 KV and at a dose of 1 × 10 ²⁰ cm ⁻² to form an ion implanted layer 41 (FIG. 4).
(A)). An epitaxial layer 43 of silicon is formed thereon, and a nitride film is deposited as a protective film 44 on the epitaxial layer and on the back surface of the silicon substrate (FIG. 4B). Then, the silicon nitride film on the backside of the semiconductor silicon substrate is selectively removed using lithography and dry etching techniques, and the backside of the semiconductor silicon substrate is etched to a boron injection layer with an ethylenediamine / pyrocatechol solution using the silicon nitride film as a mask. Etching is performed to remove all the protective film (FIG. 4C). Next, a resist pattern 45 is formed on the epi layer by using an electron beam lithography technique (FIG. 4D). Using the resist pattern 45 as a mask, the epi layer and the ion-implanted layer are etched to form a mask pattern (FIG. 4E). Further, in order to prevent charge-up due to an electron beam, gold may be deposited on the surface.

[0005] By the above method, a stencil mask used in electron beam reduction transfer lithography can be formed. However, this method requires an epitaxial technique and a high-energy ion implantation technique, which is technically very complicated and requires a long process. Furthermore, since a protective film must be deposited and a mask for blocking the electron beam only by the silicon ion-implanted layer and the epi-layer needs to be formed, the mask film thickness becomes several tens μm or more, and the Deposition and etching are also not easy.

Further, Y. Nakayama et al. Jour
nal Vacuum Science and Te
channel B8 p. 1836 (1990)
As shown in the figure, when time etching is used for etching from the back surface without using a silicon epitaxial layer, it is very difficult to control the thickness of the substrate, and it is also difficult to uniformly etch the substrate. It is. It is also difficult to vertically etch the silicon substrate by several tens of μm or more.

[0007]

As described above, in a stencil mask used for electron beam reduction transfer lithography, if only a silicon material is used, a film thickness of several tens μm or more is required. FIG. 3 shows the range of electrons in silicon with respect to the acceleration voltage of the electron beam. Normally, the acceleration voltage used in electron beam lithography is 20 to 50 keV, so that when a silicon material is used as a mask, a film thickness of about 20 μm is required. Tens of μm
It is very difficult to vertically etch silicon having the above film thickness, and many steps such as ion implantation, epitaxial, lithography, and etching techniques are required. There is a disadvantage that the process becomes complicated. Therefore, it is conceivable to reduce the silicon film thickness by depositing a metal on the surface of the silicon mask to form a multilayer film. FIG. 3 also shows the range of electrons in the case of tungsten or gold as in the case of silicon. Since gold cannot be etched, it can only be deposited on the mask surface and is very difficult to handle as an impurity in semiconductor silicon processes. Further, when the mask is irradiated with an electron beam, heat is generated and the mask is deformed. At this time, the coefficient of thermal expansion is 2.5 × 10 ⁻⁶ / deg. Is 1
4.2 a × 10 ^-6 / deg, and the thermal conductivity silicon 1.7Cm.Deg, gold is 3.1Cm.Deg, by depositing gold on the surface of the silicon mask, the mask is distorted It can be considered. In addition, the use of a multilayer film complicates the process. That is, it is desired that the stencil mask be as thin as possible, have mechanical strength, good dimensional stability and thermal stability due to temperature changes, and be formed by a simple process.

In order to solve these problems, the present inventors have completed a method of forming a stencil mask for reduced batch transfer lithography of a charged particle beam and an electron beam.

[0009]

According to the stencil mask forming method of the present invention, etching is performed from the back surface of a substrate such as semiconductor silicon by using, for example, an electric discharge machining technique using a thick electrode rod having a diameter of 5 to 50 μm. Selectively, for example, a step of thinning the substrate to a thickness of 10 to 100 μm, and selectively removing the substrate from the surface of the thinned substrate by using an electric discharge machining technique using a thin electrode rod having a diameter of 10 μm or less. Etching and vertically penetrating the thinned substrate to form a transmission hole mask pattern. Preferably, the method is characterized in that the substrate is a semiconductor substrate or a metal substrate.

Further, the present invention provides a method for selectively etching a substrate such as a semiconductor silicon or the like from the surface of the substrate by using an electric discharge machining technique using a thin electrode rod having a diameter of 10 μm or less, for example. Depth, for example, 10-100μ
forming a pattern having a vertical cross-sectional shape of m.
From the back surface of the substrate, etching is performed by using an electric discharge machining technique using a thick electrode rod having a diameter of 5 to 50 μm, the substrate is selectively thinned, and a pattern formed on the substrate is penetrated to form a transmission hole mask. Forming a pattern. And
Preferably, there is provided a method, wherein the substrate is a semiconductor substrate or a metal substrate.

That is, the present invention processes a substrate made of silicon, metal or the like by using only an electric discharge machining technique without using a lithography technique, thereby easily forming a transmission hole mask pattern having a cross section perpendicular to the substrate. Can be formed. When processing silicon by electric discharge machining, it is possible to have an aspect ratio of about 20.
Further, it is possible to form a pattern having a pattern dimension of 3 μm or less. For example, in the case of 1/50 reduction exposure, to form a 0.1 μm resist pattern, a 5 μm pattern may be created as a mask, and a film thickness for blocking an electron beam may be used. , 2
A thickness of about 0 μm is sufficient. Further, since the back surface etching of the semiconductor silicon substrate is performed by using the electric discharge machining technique instead of the wet etching, the film thickness can be controlled with good controllability. By doing so, a single silicon substrate can be used, and a stencil mask that is not thermally distorted can be formed. Further, the electric discharge machining technique can be applied to metals such as tungsten and stainless steel, and a stencil mask can be easily formed by using these.

[0012]

According to the present invention, an accurate stencil mask for electron beam reduced batch transfer lithography can be easily formed by the above-mentioned stencil mask forming process without causing a thin film and distortion due to heat. In particular, since the mask pattern is formed using only the electric discharge machining technique, the mask pattern can be formed very easily. A stencil mask can be easily formed without the necessity of vapor deposition. Also, by using this electric discharge machining technique, a pattern having a vertical cross-sectional shape can be easily formed. That is, by using the electric discharge machining technique, it is possible to easily form an accurate stencil mask having excellent mechanical strength, good dimensional stability due to temperature change, and good thermal stability. Further, in the etching of the back surface of the substrate, by performing the electric discharge machining technique from the back surface, the required film thickness of the substrate can be controlled with good controllability, and a thin film substrate can be easily obtained. Therefore, by using the present invention, it is possible to effectively form a thin stencil mask having accurate and excellent thermal stability.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the outline of the present invention will be described. The present invention can easily form a thin, highly practical stencil mask having no thermal strain by using an electric discharge machining technique for a silicon material or a metal material alone. 1-1 on silicon substrate by electric discharge machining
Since the 0 μm pattern is opened, an accurate pattern having a vertical cross-sectional shape can be formed. Further, in order to block the electron beam, the film thickness is desirably 30 μm.
m, for example, only a silicon substrate of about 20 to 30 μm is left. At this time, since the thinning of silicon by etching the back surface of the silicon substrate is also performed by using the electric discharge machining technique, a desired silicon film thickness can be easily obtained with high accuracy. In addition, since they are formed as a single unit, they are not distorted by the influence of heat due to the electron beam. In addition, since EDM technology is used, in addition to semiconductor silicon materials, it can be used for metal materials such as tungsten and stainless steel, so patterns can be easily and accurately formed as stencil masks for electron beam reduction batch transfer lithography. can do.

Hereinafter, a method of forming a stencil mask according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a process sectional view of a stencil mask forming method according to an embodiment of the present invention. Using stainless steel 11 having a thickness of about 300 μm as a substrate,
Using the electric discharge machining electrode 12 having a diameter of about 10 μm from the back surface of the substrate, etching was selectively performed up to a portion indicated by a broken line 50 by an electric discharge machining technique (FIG. 1A).
The back surface etching was performed by this electric discharge machining technique to make the stainless steel into a thin film of about 10 μm. Using the electric discharge machining electrode 13 having a diameter of about 3 μm from the surface of the thin film substrate, etching was selectively performed by electric discharge machining technology to form a pattern (FIG. 1B). Further, the etching is advanced with the electrode for electric discharge machining, the stainless steel substrate is penetrated, and a penetrating portion 100 having a vertical cross-sectional shape is formed. It was possible to form a stencil mask having excellent strength, high thermal stability and no distortion due to heat (FIG. 1C).

As described above, according to the present embodiment, by using the electric discharge machining technique on a single stainless steel substrate,
The stencil mask processing process can be greatly simplified, and even when the electron beam acceleration voltage is 50 keV, a practical stencil mask for electron beam reduction batch transfer lithography with excellent thermal stability and without heat distortion. Can be formed. Further, here, by performing back surface etching from the back surface of the stainless steel substrate using the electric discharge machining technique, the film thickness can be controlled with good controllability. Further, since the electric discharge machining technique is used, a stencil mask can be formed using a simple metal such as tungsten or iron, a semiconductor silicon substrate, or the like, in addition to the stainless steel substrate.

Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. (FIG. 2) is a process sectional view of a stencil mask forming method according to a second embodiment of the present invention. From the surface of the semiconductor silicon substrate 21,
Using an electric discharge machining technique, an electric discharge machining electrode 22 having a diameter of 4 μm.
Then, the silicon substrate was etched to form a pattern 51 (FIG. 2A). Further, etching was performed to a depth of about 20 to 30 μm with this electrode for electric discharge machining.
Thereafter, using a discharge machining electrode 23 having a diameter of about 10 μm from the back surface of the semiconductor silicon substrate, etching was selectively performed to a portion indicated by a broken line 52 by a discharge machining technique (FIG. 2B). Using this electric discharge machining technique, the semiconductor silicon substrate is etched from the back surface to penetrate the pattern formed on the silicon substrate, and the penetrating portion 100 is formed. A stencil mask having excellent strength, high thermal stability and free from distortion due to heat was formed (FIG. 2C).

As described above, according to the present embodiment, the stencil mask processing step can be greatly simplified by using the electric discharge machining technique for the semiconductor silicon substrate alone, and the acceleration voltage of the electron beam is 50 keV. Even in this case, it is possible to form a practical stencil mask for electron beam reduction batch transfer lithography having excellent thermal stability and no distortion due to heat. Further, by performing etching from the back surface of the semiconductor silicon substrate by using the electric discharge machining technique, the film thickness can be controlled with good controllability. Further, since the electric discharge machining technique is used, a stencil mask can be formed using a simple metal such as tungsten or stainless steel in addition to the silicon substrate.

[0019]

As described above, according to the present invention,
A stencil mask for electron beam reduction batch transfer lithography can be easily manufactured by forming a mask pattern from the surface of a substrate such as semiconductor silicon using an electric discharge machining technique. In particular, since the mask pattern is formed by using the electric discharge machining technique, an accurate stencil mask having a vertical sectional shape can be easily formed. Further, by using the semiconductor silicon substrate alone, an accurate, thin, highly practical stencil mask having excellent mechanical strength, high thermal stability, free from thermal distortion, can be easily formed. In addition, using the EDM technology in the backside etching,
Since the thin film substrate is formed, the mask film thickness can be easily controlled with good controllability. In addition, since EDM technology is used, a mask pattern can be easily formed even when using a simple metal such as tungsten or stainless steel in addition to a silicon substrate, and a stencil mask for electron beam reduced batch transfer lithography. And effectively contribute to the manufacture of ultra-high density integrated circuits.

[Brief description of the drawings]

FIG. 1 is a process sectional view of a stencil mask forming method according to a first embodiment of the present invention;

FIG. 2 is a process sectional view of a stencil mask forming method according to a second embodiment of the present invention.

FIG. 3 is a diagram showing an electron range with respect to an acceleration voltage of an electron beam.

FIG. 4 is a process sectional view of a conventional stencil mask forming method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Stainless steel 12 Electrode for electrical discharge machining 21 Semiconductor silicon substrate 100 Penetration part

Continuation of front page (56) References JP-A-4-196209 (JP, A) JP-A-5-217876 (JP, A) JP-A-4-370918 (JP, A) JP-A-4-240719 (JP) , A) (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/027

Claims (4)

(57) [Claims] A step of selectively thinning the substrate by etching from the back surface of the substrate by using an electric discharge machining technique using a thick electrode rod; Selectively etching the substrate using the used electric discharge machining technique and forming a transmission hole pattern by penetrating the thinned substrate. 2. The method according to claim 1, wherein the substrate is a semiconductor substrate or a metal substrate, and the thickness of the substrate when thinned is 10 μm to 100 μm.
2. The method according to claim 1, wherein m is m. 3. A step of selectively etching the substrate from the surface of the substrate by using an electric discharge machining technique using thin electrode rods to form a pattern;
Forming a through-hole mask pattern by etching using an electric discharge machining technique using a thick electrode rod, selectively thinning the substrate, and penetrating the pattern formed on the substrate. A stencil mask forming method. 4. The method according to claim 1, wherein the substrate is a semiconductor substrate or a metal substrate, and the substrate has a thickness of 10 μm to 100 μm when thinned.
4. The method according to claim 3, wherein m is m.